Tonometry Based Blood Pressure Measurements Using a Two-Dimensional Force Sensor Array

ABSTRACT

Representative methods, apparatus and systems are disclosed for blood pressure and other vital sign monitoring using arterial applanation tonometry, including ambulatory blood pressure and other vital sign monitoring. A representative system comprises a wearable apparatus. The various embodiments measure blood pressure and other vital sign monitoring using a plurality of pressure sensors of a pressure sensor array, with one or more of the pressure sensors  140  applanating an artery, such as a radial artery. In a first embodiment, a pressure sensor signal is utilized which has the highest cross-coherence with the signals of its nearest pressure sensor neighbors of the pressure sensor array. In a second embodiment, Kalman filtering is utilized for the pressure sensor signals from the pressure sensor array.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a nonprovisional of and claims the benefit of andpriority to U.S. Provisional Patent Application No. 62/355,017, filedJun. 27, 2016, inventors Sanjay Mehrotra et al., titled “Tonometry BasedBlood Pressure Measurements Using a Two-Dimensional Force Sensor Array”,and further is a nonprovisional of and claims the benefit of andpriority to U.S. Provisional Patent Application No. 62/375,524, filedAug. 16, 2016, inventors Sanjay Mehrotra et al., titled “Tonometry BasedBlood Pressure Measurements Using a Two-Dimensional Force Sensor Array”,which are commonly assigned herewith, and all of which are herebyincorporated herein by reference in their entireties with the same fullforce and effect as if set forth in their entireties herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under U01 EB020589awarded by the National Institutes of Health. The government has certainrights in the invention.

FIELD OF THE INVENTION

The present invention, in general, relates to blood pressure and othervital sign monitoring, and more particularly, relates to an apparatus,system and method for noninvasive, ambulatory blood pressure and vitalsign monitoring.

BACKGROUND OF THE INVENTION

High blood pressure (“BP”), also referred to as hypertension, is a majorcardiovascular risk factor contributing to various medical conditions,diseases, and events such as heart attacks, heart failure, aneurisms,strokes, and kidney disease, for example. While hypertension generallyis medically treatable, the rates for detection and control of high BPremain low, especially because high BP may not cause any other symptomswhich would be noticeable to an individual. As a result, there is awell-established need for blood pressure and other vital signmonitoring, whether such monitoring occurs in a hospital setting, aphysician's office, a patient's home or office, and whether suchmonitoring occurs while the individual is at rest or engaged in anactivity, such as sitting, walking, exercising, or sleeping, also forexample.

Hypertension is estimated to cause 7.5 million yearly deaths, about12.8% of all deaths [1] worldwide. In today's clinical practice, bloodpressure (BP) is typically measured in an office setting usingcuff-based devices. Despite training, such devices can be cumbersome anddifficult to use. Office-based blood pressure has limited sensitivity(75%) and specificity (75%) as a sole test for diagnosing hypertension,and studies have shown that ambulatory blood pressure predicts mortalitysignificantly better than clinical blood pressure [3]. Clinical practiceguidelines and professional organizations increasingly emphasize 24-hourambulatory blood pressure monitoring and home-based self-monitoring ofblood pressure to aid in the diagnosis and management of hypertension[3, 4]. Cuff-based BP measurement systems are cumbersome for ambulatoryand everyday use. The force-pressure measurement principles ofapplanation tonometry are well established (see, e.g. [4]) and date backto the 1960s with the creation of a simple, single transducer [5].

CITED REFERENCES

-   [1] Raised Blood Pressure. [cited 2013 September]; Available from:    http://www.who.int/gho/ncd/risk_factors/blood_pressure_prevalence_text/en/.-   [2] NICE, UK National Institute for Health and Care Excellence. NICE    clinical guideline 127. Hypertension: clinical management of primary    hypertension in adults. 2011.-   [3] Drzewiecki, G. M., J. Melbin, and A. Noordergraaf, Arterial    tonometry: review and analysis. Journal of biomechanics, 1983.    16(2): p. 141-152.-   [4] Pressman, G. L. and P. M. Newgard, A Transducer for the    Continuous External Measurement of Arterial Blood Pressure. IEEE    Trans Biomed Eng, 1963. 10: p. 73-81.-   [5] Joseph S Eckerle, Tonometry, arterial, in Encyclopedia of    medical devices and instrumentation. 2006.

BRIEF SUMMARY OF THE INVENTION

The representative embodiments of the present invention provide numerousadvantages. The disclosed invention uses a signal and data processingapproach that can be used for ambulatory blood pressure measurement. Thesignal and data processing approach uses a two-dimensional array ofpressure sensors for applanating an artery and combines the informationgenerated from these pressure sensors to estimate an individual'sambulatory blood pressure. The two-dimensional array of pressure sensorsincreases the likelihood of obtaining accurate pressure sensor data froman applanated artery. The approach is particularly advantageous in anambulatory setting, where it may be difficult to locate an individual'sartery, and the signals generated may be noisy.

A representative method embodiment for determining a blood pressure of asubject human being for ambulatory monitoring is disclosed, with therepresentative method comprising: using a pressure sensor array having aplurality of pressure sensors spaced-apart in at least two dimensions,applanating an artery; receiving a plurality of pressure sensor signals,one or more of the pressure sensor signals having data representingamplitudes of one or more arterial pressure waves; determining afrequency content of each of the one or more of the pressure sensorsignals having data; selecting one or more periodic pressure sensorsignals to form a first plurality of selected pressure sensor signals;selecting one or more periodic pressure sensor signals within a selectedor predetermined deviation, such as a standard deviation, of a mean ofthe first plurality of selected pressure sensor signals to form a secondplurality of selected pressure sensor signals; using one or moreperiodic pressure sensor signals from the second plurality of selectedpressure sensor signals, determining a systolic blood pressure value anda diastolic blood pressure value.

A representative method may further comprise: for each periodic pressuresensor signal of the second plurality of selected pressure sensorsignals, determining a cross-coherence with each nearest neighborpressure sensor signal; and selecting a periodic pressure sensor signalhaving a highest mean cross-coherence. For such a representativeembodiment, the step of determining the systolic blood pressure valueand the diastolic blood pressure value may further comprise: determiningthe systolic blood pressure value as a maximum of the periodic pressuresensor signal having a highest mean cross-coherence; and determining thediastolic blood pressure value as a minimum of the periodic pressuresensor signal having a highest mean cross-coherence.

A representative method may further comprise: determining the mean andstandard deviation of the first plurality of selected pressure sensorsignals.

A representative method also may further comprise: performing a firstfiltering of the plurality of pressure sensor signals to eliminate oneor more pressure sensor signals below a selected or predeterminedthreshold, such as those which do not have relevant pressure data.

A representative method may further comprise: sampling and convertingthe plurality of pressure sensor signals into a corresponding pluralityof digital amplitude values.

A representative method may further comprise: using one or more periodicpressure sensor signals from the second plurality of selected pressuresensor signals, determining a heart rate.

A representative method may further comprise: performing a Kalmanfiltering of the second plurality of selected pressure sensor signals;determining the systolic blood pressure value as a maximum of the Kalmanfilter data; and determining the diastolic blood pressure value as aminimum of the Kalman filter data.

A representative method may further comprise one or more of thefollowing: displaying the determined blood pressure value and othervital sign information to the user; transmitting the determined bloodpressure value and other vital sign information to a central location;and/or storing the determined blood pressure value and other vital signinformation in a memory circuit.

A representative apparatus embodiment is disclosed for determining ablood pressure of a subject human being for ambulatory monitoring, therepresentative apparatus embodiment comprising: a pressure sensor arrayhaving a plurality of pressure sensors spaced-apart in at least twodimensions; and a processor coupled to the pressure sensor array, theprocessor adapted to receive a plurality of pressure sensor signals, oneor more of the pressure sensor signals having data representingamplitudes of one or more arterial pressure waves; determine a frequencycontent of each of the one or more of the pressure sensor signals havingdata; select one or more periodic pressure sensor signals to form afirst plurality of selected pressure sensor signals; select one or moreperiodic pressure sensor signals within a selected or predetermineddeviation, such as a standard deviation, of a mean of the firstplurality of selected pressure sensor signals to form a second pluralityof selected pressure sensor signals; and using one or more periodicpressure sensor signals from the second plurality of selected pressuresensor signals, determine a systolic blood pressure value and adiastolic blood pressure value.

A representative apparatus embodiment may further comprise: a housingcoupled to the pressure sensor array and to the processor; and awearable attachment coupled to the housing.

In a representative apparatus embodiment, the processor may be furtheradapted, for each periodic pressure sensor signal of the secondplurality of selected pressure sensor signals, to determine across-coherence with each nearest neighbor pressure sensor signal; andselect a periodic pressure sensor signal having a highest meancross-coherence. For such a representative apparatus embodiment, theprocessor may be further adapted to determine the systolic bloodpressure value as a maximum of the periodic pressure sensor signalhaving a highest mean cross-coherence; and determine the diastolic bloodpressure value as a minimum of the periodic pressure sensor signalhaving a highest mean cross-coherence.

In a representative apparatus embodiment, the processor may be furtheradapted to determine the mean and standard deviation of the firstplurality of selected pressure sensor signals.

In a representative apparatus embodiment, the processor may be furtheradapted to perform a first filtering of the plurality of pressure sensorsignals to eliminate one or more pressure sensor signals below aselected or predetermined threshold.

A representative apparatus may further comprise: an analog-to-digitalconverter to sample and convert the plurality of pressure sensor signalsinto a corresponding plurality of digital amplitude values.

In a representative apparatus embodiment, the processor may be furtheradapted, using one or more periodic pressure sensor signals from thesecond plurality of selected pressure sensor signals, to determine aheart rate.

In a representative apparatus embodiment, the processor may be furtheradapted to perform a Kalman filtering of the second plurality ofselected pressure sensor signals; determine the systolic blood pressurevalue as a maximum of the Kalman filter data; and determine thediastolic blood pressure value as a minimum of the Kalman filter data.

A representative apparatus may further comprise: a display fordisplaying the determined blood pressure value and other vital signinformation to the user. A representative apparatus also may furthercomprise: a wireless transmitter to transmit the determined bloodpressure value and other vital sign information to a central location. Arepresentative apparatus also may further comprise: a network interfacecircuit to transmit the determined blood pressure value and other vitalsign information to a central location. A representative apparatus alsomay further comprise: a memory circuit storing the determined bloodpressure value and other vital sign information in a memory circuit.

A representative system embodiment is disclosed for determining a bloodpressure of a subject human being for ambulatory monitoring, therepresentative system embodiment comprising: a wearable apparatus and acentral monitor.

In such a representative system embodiment, the wearable apparatus maycomprise: a pressure sensor array having a plurality of pressure sensorsspaced-apart in at least two dimensions, the pressure sensor arraygenerating a plurality of pressure sensor signals, one or more of thepressure sensor signals having data representing amplitudes of one ormore arterial pressure waves; and a wireless transmitter coupled to thepressure sensor array to transmit the plurality of pressure sensorsignals.

In such a representative system embodiment, the central monitor maycomprise: a memory circuit; a wireless transceiver to receive thetransmitted plurality of pressure sensor signals; and a processorcoupled to the wireless transceiver and to the memory, the processoradapted to a processor coupled to the pressure sensor array, theprocessor adapted to determine a frequency content of each of the one ormore of the pressure sensor signals having data; select one or moreperiodic pressure sensor signals to form a first plurality of selectedpressure sensor signals; select one or more periodic pressure sensorsignals within a selected or predetermined deviation, such as a standarddeviation, of a mean of the first plurality of selected pressure sensorsignals to form a second plurality of selected pressure sensor signals;and using one or more periodic pressure sensor signals from the secondplurality of selected pressure sensor signals, determine a systolicblood pressure value and a diastolic blood pressure value.

In such a representative system embodiment, the wearable apparatus mayfurther comprise: a housing coupled to the pressure sensor array; and awearable attachment coupled to the housing.

In a representative system embodiment, the processor may be furtheradapted, for each periodic pressure sensor signal of the secondplurality of selected pressure sensor signals, to determine across-coherence with each nearest neighbor pressure sensor signal; andselect a periodic pressure sensor signal having a highest meancross-coherence. In such a representative system embodiment, theprocessor may be further adapted to determine the systolic bloodpressure value as a maximum of the periodic pressure sensor signalhaving a highest mean cross-coherence; and determine the diastolic bloodpressure value as a minimum of the periodic pressure sensor signalhaving a highest mean cross-coherence.

In a representative system embodiment, the processor may be furtheradapted to determine the mean and standard deviation of the firstplurality of selected pressure sensor signals.

In a representative system embodiment, the processor may be furtheradapted to perform a first filtering of the plurality of pressure sensorsignals to eliminate one or more pressure sensor signals below aselected or predetermined threshold.

In such a representative system embodiment, the wearable apparatus mayfurther comprise: an analog-to-digital converter to sample and convertthe plurality of pressure sensor signals into a corresponding pluralityof digital amplitude values.

In a representative system embodiment, the processor may be furtheradapted, using one or more periodic pressure sensor signals from thesecond plurality of selected pressure sensor signals, to determine aheart rate.

In a representative system embodiment, the processor may be furtheradapted to perform a Kalman filtering of the second plurality ofselected pressure sensor signals; determine the systolic blood pressurevalue as a maximum of the Kalman filter data; and determine thediastolic blood pressure value as a minimum of the Kalman filter data.

In a representative system embodiment, the wearable apparatus mayfurther comprise: a display for displaying the determined blood pressurevalue and other vital sign information to the user.

In a representative system embodiment, the wireless transceiver isconfigured to transmit the determined blood pressure value and othervital sign information to a central location.

In a representative system embodiment, the central monitor may furthercomprise: a network interface circuit to transmit the determined bloodpressure value and other vital sign information to a central location.

In a representative system embodiment, the memory circuit may also storethe determined blood pressure value and other vital sign information.

Another representative method embodiment for determining a bloodpressure of a subject human being for ambulatory monitoring isdisclosed, with the representative method comprising: using a pressuresensor array having a plurality of pressure sensors spaced-apart in atleast two dimensions, applanating an artery; receiving a plurality ofpressure sensor signals, one or more of the pressure sensor signalshaving data representing amplitudes of one or more arterial pressurewaves; filtering the plurality of pressure sensor signals to eliminateone or more pressure sensor signals below a selected or predeterminedthreshold; performing a Fourier transformation to determine a frequencycontent of each of the one or more of the pressure sensor signals havingdata; selecting one or more periodic pressure sensor signals to form afirst plurality of selected pressure sensor signals, the one or moreperiodic pressure sensor signals having a frequency between 0.5 to 3.5Hz; determining the mean and standard deviation of the first pluralityof selected pressure sensor signals; selecting one or more periodicpressure sensor signals within a selected or predetermined deviation,such as a standard deviation, of the mean of the first plurality ofselected pressure sensor signals to form a second plurality of selectedpressure sensor signals; for each periodic pressure sensor signal of thesecond plurality of selected pressure sensor signals, determining across-coherence with each nearest neighbor pressure sensor signal;selecting a periodic pressure sensor signal having a highest meancross-coherence; determining a systolic blood pressure value as amaximum of the periodic pressure sensor signal having a highest meancross-coherence; determining a diastolic blood pressure value as aminimum of the periodic pressure sensor signal having a highest meancross-coherence; and displaying the determined blood pressure value andother vital sign information to the user.

Another representative apparatus embodiment is disclosed for determininga blood pressure of a subject human being for ambulatory monitoring, therepresentative apparatus embodiment comprising: a display; a memory; apressure sensor array having a plurality of pressure sensorsspaced-apart in at least two dimensions; and a processor coupled to thepressure sensor array, to the display and to the memory, the processoradapted to receive a plurality of pressure sensor signals, one or moreof the pressure sensor signals having data representing amplitudes ofone or more arterial pressure waves; filtering the plurality of pressuresensor signals to eliminate one or more pressure sensor signals below aselected or predetermined threshold; perform a Fourier transformation todetermine a frequency content of each of the one or more of the pressuresensor signals having data; select one or more periodic pressure sensorsignals to form a first plurality of selected pressure sensor signals,the one or more periodic pressure sensor signals having a frequencybetween 0.5 to 3.5 Hz; determine the mean and standard deviation of thefirst plurality of selected pressure sensor signals; select one or moreperiodic pressure sensor signals within a selected or predetermineddeviation, such as a standard deviation, of the mean of the firstplurality of selected pressure sensor signals to form a second pluralityof selected pressure sensor signals; for each periodic pressure sensorsignal of the second plurality of selected pressure sensor signals,determine a cross-coherence with each nearest neighbor pressure sensorsignal; select a periodic pressure sensor signal having a highest meancross-coherence; determine a systolic blood pressure value as a maximumof the periodic pressure sensor signal having a highest meancross-coherence; determine a diastolic blood pressure value as a minimumof the periodic pressure sensor signal having a highest meancross-coherence; and provide the systolic blood pressure value and thediastolic blood pressure value to the display.

Numerous other advantages and features of the present invention willbecome readily apparent from the following detailed description of theinvention and the embodiments thereof, from the claims and from theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will bemore readily appreciated upon reference to the following disclosure whenconsidered in conjunction with the accompanying drawings, wherein likereference numerals are used to identify identical components in thevarious views, and wherein reference numerals with alphabetic charactersare utilized to identify additional types, instantiations or variationsof a selected component embodiment in the various views, in which:

FIG. 1 is a plan view diagram illustrating representative first and/orsecond apparatus embodiments with a wearable wristband attachmentattached to a wrist of an individual subject.

FIG. 2 is a cross-sectional view diagram illustrating representativefirst and/or second apparatus embodiments with a wearable wristbandattachment attached to a wrist of an individual subject of FIG. 1 withapplanation of a radial artery.

FIG. 3 is a block diagram of representative first apparatus and firstsystem embodiments.

FIG. 4 is a block diagram of representative second apparatus and secondsystem embodiments.

FIG. 5 is a block diagram of a representative pressure sensor array.

FIGS. 6A, 6B and 6C (collectively referred to as FIG. 6) is a flow chartof a representative first method embodiment for the determination ofsystolic and diastolic blood pressure values, heart rate and other vitalsigns.

FIGS. 7A and 7B (collectively referred to as FIG. 7) is a flow chart ofa representative second method embodiment for the determination ofsystolic and diastolic blood pressure values, heart rate and other vitalsigns.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

While the present invention is susceptible of embodiment in manydifferent forms, there are shown in the drawings and will be describedherein in detail specific exemplary embodiments thereof, with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the invention to the specific embodiments illustrated. In thisrespect, before explaining at least one embodiment consistent with thepresent invention in detail, it is to be understood that the inventionis not limited in its application to the details of construction and tothe arrangements of components set forth above and below, illustrated inthe drawings, or as described in the examples. Methods and apparatusesconsistent with the present invention are capable of other embodimentsand of being practiced and carried out in various ways. Also, it is tobe understood that the phraseology and terminology employed herein, aswell as the abstract included below, are for the purposes of descriptionand should not be regarded as limiting.

As mentioned above and as discussed in greater detail below, therepresentative apparatus, system and method provide for noninvasive,ambulatory blood pressure and other vital sign monitoring. Other vitalsigns may also be determined, including without limitation heart rate,cardiac output, and stroke volume.

FIG. 1 is a plan view diagram illustrating representative first and/orsecond apparatus 100, 300 embodiments with a wearable wristbandattachment attached to a wrist 50 of an individual subject. FIG. 2 is across-sectional view (through the C-C′ plane) illustratingrepresentative first and/or second apparatus 100, 300 embodiments with awearable wristband attachment attached to a wrist 50 of an individualsubject of FIG. 1 with applanation of a radial artery 60. FIG. 3 is ablock diagram of representative first apparatus 100 and first system 200embodiments. FIG. 4 is a block diagram of representative secondapparatus 300 and second system 400 embodiments. FIG. 5 is a blockdiagram of a representative pressure sensor array 110.

As illustrated in FIGS. 1 and 2, the representative first and/or secondapparatus 100, 300 embodiments provide a predetermined or potentiallyvariable amount of pressure to the wrist 50 of an individual subject toapplanate the artery 60, slightly flattening the artery (from agenerally more circular cross-section, illustrated using dashed lines)and generally decreasing its diameter from “A” to a smaller diameter“B”, but without occluding the artery. With such applanation, one ormore pressure sensors 140 of the pressure sensor array 110 of therepresentative first and/or second apparatus 100, 300 embodiments isarranged or positioned substantially over the artery 60 to detect and/ormeasure pressure from the applanated artery 60 and the surroundingtissue. More specifically, one or more pressure sensors 140 the pressuresensor array 110 will generally be positioned substantially over theflattened portion of the applanated artery 60, so that the entire areaof the one or more pressure sensors 140 is arranged substantially overthe flattened portion of the applanated artery 60 for accurate pressuremeasurements, while other pressure sensors 140 of the pressure sensorarray 110 may be positioned medially or laterally from the applanatedartery 60.

FIG. 3 is a block diagram of representative first apparatus 100 andfirst system 200 embodiments. As illustrated in FIG. 3, a firstapparatus 100 is utilized in the first system 200 to acquire pressuremeasurements or data, from locations or positions over an artery in theneck, lower or upper extremities, or other accessible regions of theindividual, utilized in BP measurements or determinations, such aspositioned over the radial artery 60 as discussed above. The firstsystem 200 further comprises a central monitor 150, which receives thepressure measurements or data from the first apparatus 100, performssignal and data processing, and generates corresponding estimates ormeasurements of blood pressure and other vital signs, as mentionedabove.

It should be noted that the central monitor 150 is “central” in thesense of being the main, predominant or principal receivers of thesignals from the apparatus 100, and the provider of correspondingestimates of measurements of blood pressure and other vital signs, andnot “central” in terms of determining a “central blood pressure”.

The first apparatus 100 comprises a pressure sensor array 110, ananalog-to-digital converter (ADC) 115, and a wireless transmitter 135.The pressure sensor array 110 comprises a plurality of spaced-apartpressure sensors 140 arranged or disposed in an array (as illustrated inFIG. 5), each of which senses pressure (as a force transducer having acorresponding area), and generates a corresponding pressure sensor 140signal which is indicative of an arterial pressure when positioned overan artery. The pressure sensor array 110, an analog-to-digital converter(ADC) 115, and a wireless transmitter 135 are typically arranged ordisposed within a housing 185. The corresponding pressure sensor 140signal may be an analog pressure sensor (electrical) signal, and if so,the analog-to-digital converter (ADC) 115 samples the analog pressuresensor signals from each of the pressure sensors 140 of the pressuresensor array 110 and generates a stream or series of correspondingdigital amplitude values, each of which is indicative of or representsthe amplitude of one or more arterial pressure waves occurring duringthe sampling time interval. Alternatively, the corresponding pressuresensor 140 signal may be provided as a digital amplitude value, alsowhich is indicative of or represents the amplitude of one or morearterial pressure waves occurring during the sampling time interval, andin which case, the analog-to-digital converter (ADC) 115 may be omittedas a separate component in the first and/or second apparatus 100, 300.The wireless transmitter 135 wirelessly transmits the correspondingstream or series of corresponding digital amplitude values to thecentral monitor 150.

Optionally, the first apparatus 100 may also include a controller 160and a wearable attachment 155. When included, the wearable attachment155 may be a wristband, an adhesive patch, a band for an upper or lowerpart of an arm or leg, or a ring for a finger, all for example andwithout limitation. In other embodiments which do not include a wearableattachment 155, the housing 185 may have any suitable form factor, e.g.,as any type of portable device, such as a handheld device, andoptionally may also include one or more components of the centralmonitor 150, also for example and without limitation. Other types ofsensors may also be included in the first and/or second apparatus 100,300. When a controller 160 is included, the controller 160 combines thestream or series of corresponding digital values (indicative of thearterial pressure waves), from each pressure sensor 140 of the pressuresensor array 110, along with any other sensor data, for wirelesstransmission by the wireless transmitter 135 to the central monitor 150.

The central monitor 150 generally comprises a wireless transceiver (orreceiver with or without a transmitter) 165, a processor 120, a memory125, a network interface circuit 130, and a user input and output device190, such as a touch screen display 195 or any other type of visualdisplay, for example. The memory 125 generally stores calibration data,as discussed in greater detail below, such as for any offset or scaling,and may also store collected data and corresponding results, such aspressure measurements or determinations and corresponding estimates ormeasurements of the BP and other vital signs of the individual. Thewireless transceiver 165, which may be included in the network interfacecircuit 130, receives the stream or series of corresponding digitalamplitude values indicative of or representing the arterial pressurewaves, from the first apparatus 100, and provides or transfers this datato the processor 120. Using this stream or series of correspondingdigital amplitude values (indicative of or representing the arterialpressure waves), the processor 120 generates the pressure measurementsor determinations and corresponding estimates or measurements of the BPand other vital signs of the individual. As discussed in greater detailbelow with reference to the flow charts of FIGS. 6 and 7, the processor120 may also be considered to include, such as through configuration orprogramming, one or more filters 170, a fast Fourier transform (ordiscrete Fourier transform) circuit or block 175, and a digital signalprocessor (“DSP”) or DSP block 180.

The processor 120 may then provide the estimates or measurements of theBP and other vital signs of the individual to the user input and outputdevice 190, such as for display to the individual on a touch screendisplay 195. The processor 120 also may then provide the estimates ormeasurements of the BP and other vital signs of the individual to thenetwork interface circuit 130, such as for transmission of the estimatesor measurements of the BP and other vital signs of the individual toanother location or device, such as to a hospital or clinic computingsystem, also for example and without limitation.

Not separately illustrated in FIG. 3, those having skill in the art willrecognize that devices such as central monitor 150 and first apparatus100 also generally include clocking circuitry and distribution, and apower supply with power distribution, which may be a battery or otherenergy source, for example and without limitation.

It should be noted that various features and physiological changes oraspects of an individual and/or the arteries of an individual, such asskin and vessel elasticity or stiffness, the movement of the individual,and potentially also the contact pressure exerted by the first apparatus100 (and/or second apparatus 300) on the subject individual, may alsoaffect the measurement of the amplitude of the arterial pressure wavesand resulting pressure measurements or determinations, withoutcorresponding changes in the subject's absolute BP. These pressures maybe measured or otherwise determined, such as during a calibrationprocess, and utilized to provide offsets and/or scaling of the measuredBP magnitudes, discussed in greater detail below with reference to FIGS.6 and 7.

Referring to FIG. 4, a second system 400 generally comprises a secondapparatus 300, and any central monitor 150 is merely optional. Asillustrated in FIG. 4, a second apparatus 300 is utilized in the secondsystem 400 to acquire pressure measurements or data, from locations orpositions over an artery in the neck, lower or upper extremities, orother accessible regions of the individual, utilized in BP measurementsor determinations, such as positioned over the radial artery 60 asdiscussed above. For example and without limitation, in a second system400, a second apparatus 300 may be worn on a left or right wrist. Thesecond apparatus 300 operates as described above for the first apparatus100 and further comprises many of the components and functionality of acentral monitor 150. Accordingly, the second apparatus 300 also performssignal and data processing, and generates corresponding estimates ormeasurements of blood pressure and other vital signs, as mentionedabove, as discussed above.

The second system 400 may be viewed as combining the components andfunctionality of many (but generally not all) the components andfunctions of the first system 200 into one device (as a second apparatus300), rather than distributing these components and functions betweenand among two devices (a first apparatus 100 and a central monitor 150).The second system 400 also eliminates components that could now beconsidered redundant, optional or unnecessary when selected componentsand functions of the central monitor 150 are included in the secondapparatus 300 (e.g., eliminating a controller 160 and wirelesstransmitter 135 in the second apparatus 300, and optionally eliminatinga wireless transceiver 165 and/or a network interface circuit 130 of acentral monitor 150). Accordingly, unless specified to the contrary, thecomponents of the second system 400 generally function identically tothe components of the first system 200 described above, and with thesecond apparatus 300 generally including or combining the overallfunctionality of a first apparatus 100 and a central monitor 150,without redundancy.

The second apparatus 300 also comprises a pressure sensor array 110having one or more pressure sensors 140, and generally also ananalog-to-digital converter (ADC) 115, all of which function asdiscussed above. Optionally, the second apparatus 300 may also includeother sensors (not separately illustrated), and a wearable attachment155, all of which function as discussed above, with the variouscomponents arranged or disposed within a housing 185.

The second apparatus 300 also generally comprises a processor 120, amemory 125, and a user input and output device 190, such as a touchscreen display 195 or any other type of visual display, an on/offbutton, and so on, also for example, all of which function as discussedabove. Optionally, the second apparatus 300 may include a networkinterface circuit 130. The memory 125 of the second apparatus 300 alsogenerally stores calibration data, as discussed in greater detail below,and may also store collected data and corresponding results, such asmeasurements or determinations of the BP and other vital signs of theindividual. Optionally, the second apparatus 300 may include a wirelesstransceiver 165. The digital amplitude values indicative of orrepresenting the arterial pressure waves generated by theanalog-to-digital converter (ADC) 115, from the corresponding analogsensor electrical signal provided by corresponding pressure sensors 140of the pressure sensor array 110, or directly from the pressure sensors140 of the pressure sensor array 110, are also transferred to theprocessor 120 of the second apparatus 300. Using this stream or seriesof corresponding digital amplitude values (indicative of or representingthe arterial pressure waves, along with any other data (includingcalibration data, if any), the processor 120 of the second apparatus 300also generates the BP measurements or determinations and other vitalsigns of the individual, as discussed above. Also as discussed ingreater detail below with reference to the flow charts of FIGS. 6 and 7,the processor 120 may also be considered to include, such as throughconfiguration or programming, one or more filters 170, a fast Fouriertransform (or discrete Fourier transform) circuit or block 175, and adigital signal processor (“DSP”) or DSP block 180.

The processor 120 may then provide the estimates or measurements of theBP and other vital signs of the individual to the user input and outputdevice 190 of the second apparatus 300, such as for display to theindividual on a touch screen or other display 195. For example, in arepresentative embodiment in which the second apparatus 300 is worn on aleft or right wrist by a subject individual, using a wristband orbracelet as a wearable attachment 155, the individual's BP and othervital signs may be displayed and viewed by the user in real timesimilarly or equivalently to reading a wristwatch. Also not separatelyillustrated in FIG. 4, those having skill in the art will recognize thatdevices such as the first apparatus 100 and second apparatus 300 alsogenerally include clocking circuitry and distribution, and a powersupply with power distribution, which may be a battery or other energysource, for example and without limitation.

It should be noted that any of the systems 200, 400 may be utilized inconjunction with other devices and systems, as known in the computer andcommunications fields, such as optional relay stations or docking units,not separately illustrated. For example and without limitation, such anoptional relay station or docking unit may receive BP measurements ordeterminations from a second apparatus 300, and transfer this data to anetwork or cloud storage device (also not separately illustrated), whichalso may be accessed by physicians or other clinical staff, such asthrough a compatible portal at a hospital or a clinical computingsystem.

Referring to FIG. 5, a pressure sensor array 110 comprises a pluralityof spaced-apart pressure sensors 140, arranged or positioned as aregularly spaced array. As illustrated in FIG. 5, a plurality of “N”pressure sensors 140 are utilized, each of which generates acorresponding pressure sensor 140 signal, illustrated as pressure sensor140 signals S[0], S[1], S[2], through S[N−1], output on bus or wires 105to the ADC 115 (or directly to the controller 160 or wirelesstransmitter 135 for a first apparatus 100 or directly to a processor 120for a second apparatus 300), which may be analog or digital, asdiscussed above. In a representative embodiment, the number “N” ofpressure sensors 140 may be in the hundreds to thousands to create acomparatively dense pressure sensor array 110, such as an array of 24×24pressure sensors 140 (576 pressure sensors 140), or an array of 64×64pressure sensors 140 (4096 pressure sensors 140), or an array of 130×130pressure sensors 140 (16,900 pressure sensors 140), for example andwithout limitation. It should be noted that the pressure sensor array110 does not need to be symmetric, e.g., an array of A×B pressuresensors 140 may be utilized, such an array of 100×50 pressure sensors140 (5000 pressure sensors 140), also for example and withoutlimitation.

FIG. 6 is a flow chart of a representative first method embodiment forthe determination of systolic and diastolic blood pressure values, heartrate and other vital signs. Beginning with start step 205, an artery isapplanated, step 210, such as by applying the pressure sensor array 110against a wrist 50 and applying some pressure, which generally willapplanate a radial artery 60, for example. As each of the pressuresensors 140 generate a corresponding pressure sensor 140 signal, thepressure sensor 140 signals are sampled, step 215, and converted tocorresponding digital amplitude values (indicative of or representingthe arterial pressure waves), step 220, such as using an ADC 115, whichare provided to the processor 120 in a system 200, 400, such as throughthe wireless transmitter 135 or directly from the ADC 115.

Many of the pressure sensors 140 of the pressure sensor array 110,however, will not be positioned over the applanated artery and will notbe generating any pressure measurements or will be generating pressuremeasurements below a selected or predetermined threshold. According,using one or more filters 170, the processor 120 performs a firstfiltering, step 225, eliminating pressure sensor 140 signals below aselected or predetermined threshold, such as those which are notgenerating data (i.e., have a zero value) from further signalprocessing. The processor 120 determines the frequency content of eachpressure sensor 140 signal above the selected or predeterminedthreshold, such as those having data (a non-zero value), step 230, suchas by performing a fast Fourier transformation (“FFT”) using FFT block175. Using the frequency content, in step 235, the processor 120 selectsthose pressure sensor 140 signals which are periodic within apredetermined range to form a first plurality of selected pressuresensor 140 signals (e.g., having the most common or dominant frequency),such as those pressure sensor 140 signals which have a frequency in therange of 0.5 to 3.5 Hz, which would correspond to a heart rate of 30-210beats/minute.

The processor 120 then determines the mean (average) and standarddeviation of the first plurality of selected pressure sensor 140signals, step 240, such as using DSP block 180, and selects thosepressure sensor 140 signals from the first plurality of selectedpressure sensor 140 signals which are within a selected or predetermineddeviation, such as a standard deviation, of the mean, step 245, to forma second plurality of selected pressure sensor 140 signals, alsotypically using DSP block 180.

For each pressure sensor 140 signal of the second plurality of selectedpressure sensor 140 signals, in step 250, the processor 120 determines across-coherence of the pressure sensor 140 signal with each pressuresensor 140 signal of its nearest neighbor pressure sensors, typicallypair-wise with each pressure sensor 140 signal of eight possible nearestpressure sensor 140 neighbors of the pressure sensor array 110. For eachpressure sensor 140 signal of the second plurality of selected pressuresensor 140 signals, in step 255, the processor 120 determines the mean(average) of the cross-coherence of the pressure sensor 140 signal witheach pressure sensor 140 signal of its nearest neighbor pressure sensor140 signals, across the entire coherence spectrum. When there areadditional pressure sensor 140 signals of the second plurality ofselected pressure sensor 140 signals, step 260, the method iterates,continuing to perform steps 250 and 255 for the additional pressuresensor 140 signals.

When all of the cross-coherence determinations of steps 250 and 255 havebeen made, following step 260, the processor 120 selects a pressuresensor 140 signal having the highest (largest or greatest)cross-coherence with the pressure sensor 140 signals of its nearestpressure sensor 140 neighbors, step 265, e.g., highest averagemagnitude-squared coherence spectrum. This may also include selecting apressure sensor 140 signal having a certain or selected pattern. Theselected pressure sensor 140 signal having the highest cross-coherencethen has a high (or higher) likelihood of being properly positioned overthe applanated artery 60 and of properly or accurately detecting thecorresponding pressures of the arterial pressure waves. The processor120 then determines the maximum value from the data of the selectedpressure sensor 140 signal having the highest cross-coherence, step 270,which corresponds to or generates the systolic BP measurement ordetermination, or which may also include a calibrated offset or scalingfactor. The processor 120 then determines the minimum value from thedata of the selected pressure sensor 140 signal having the highestcross-coherence, step 275, which corresponds to or generates thediastolic BP measurement or determination, or which may also include acalibrated offset or scaling factor. Other vital signs, such as heartrate and stroke volume, or the entire BP waveform (with any calibratedoffset or scaling), may also be determined by the processor 120, step280.

When monitoring is to continue, step 285, the method iterates, returningto step 215, and otherwise, the method may end, return step 290.Alternatively, as the pressure sensors 140 may be generating pressuresensor 140 signals which are continually sampled and converted tocorresponding digital amplitude values (indicative of or representingthe arterial pressure waves), the method may iterate and return to step225, shifting a time window for examining the incoming digital datavalues.

FIG. 7 is a flow chart of a representative second method embodiment forthe determination of systolic and diastolic blood pressure values, heartrate and other vital signs. For the second method, steps 305-345correspond to steps 205-245 of the first method. Beginning with startstep 305, an artery is applanated, step 310, such as by applying thepressure sensor array 110 against a wrist 50 and applying some pressure,which generally will applanate a radial artery 60, for example. As eachof the pressure sensors 140 generate a corresponding pressure sensor 140signal, the pressure sensor 140 signals are sampled, step 315, andconverted to corresponding digital amplitude values (indicative of orrepresenting the arterial pressure waves), step 320, such as using anADC 115, which are provided to the processor 120 in a system 200, 400,such as through the wireless transmitter 135 or directly from the ADC115.

Many of the pressure sensors 140 of the pressure sensor array 110,however, also will not be positioned over the applanated artery and willnot be generating any pressure measurements or will be generatingpressure measurements below a selected or predetermined threshold, asdiscussed above. According, using one or more filters 170, the processor120 performs a first filtering, step 325, eliminating pressure sensor140 signals below a selected or predetermined threshold, such as thosewhich are not generating data (i.e., have a zero value) from furthersignal processing. The processor 120 also determines the frequencycontent of each pressure sensor 140 signal above the selected orpredetermined threshold, such as those having data (a non-zero value),step 330, such as by performing a fast Fourier transformation (“FFT”)using FFT block 175. Using the frequency content, in step 335, theprocessor 120 selects those pressure sensor 140 signals which areperiodic within a predetermined range to form a first plurality ofselected pressure sensor 140 signals (e.g., having the most common ordominant frequency), such as those pressure sensor 140 signals whichhave a frequency in the range of 0.5 to 3.5 Hz, as mentioned above,which would correspond to a heart rate of 30-210 beats/minute.

The processor 120 then determines the mean (average) and standarddeviation of the first plurality of selected pressure sensor 140signals, step 340, such as using DSP block 180, and selects thosepressure sensor 140 signals from the first plurality of selectedpressure sensor 140 signals which are within a selected or predetermineddeviation, such as a standard deviation, of the mean, step 345, to forma second plurality of selected pressure sensor 140 signals, alsotypically using DSP block 180.

For the second method, the processor 120 then performs a secondfiltering step of the second plurality of selected pressure sensor 140signals, such as performing Kalman filtering to create a “sensorfusion”, step 350, or utilizing one or more Hidden Markov Models, forexample and without limitation. Following the second filtering, theprocessor 120 then determines the maximum value from the data of thesecond filtering, step 355, which corresponds to or generates thesystolic BP measurement or determination, or which may also include acalibrated offset or scaling factor. The processor 120 also thendetermines the minimum value from the data of the second filtering, step360, which corresponds to or generates the diastolic BP measurement ordetermination, or which may also include a calibrated offset or scalingfactor.

When monitoring is to continue, step 365, the method iterates, returningto step 315, and otherwise, the method may end, return step 370.Alternatively, as the pressure sensors 140 may be generating pressuresensor 140 signals which are continually sampled and converted tocorresponding digital amplitude values (indicative of or representingthe arterial pressure waves), the method may iterate and return to step325, also shifting a time window for examining the incoming digital datavalues.

It should be noted that additional filtering may be performed for eitheror both the first and/or second methods, such as to reduce or eliminatenoise in any of the pressure sensor signals.

As used herein, a “processor” 120 or “controller” 160 may be any type ofcontroller or processor, and may be embodied as one or more processor(s)120 or controller(s) 160, configured, designed, programmed or otherwiseadapted to perform the functionality discussed herein. As the termcontroller or processor is used herein, a processor 120 or controller160 may include use of a single integrated circuit (“IC”), or mayinclude use of a plurality of integrated circuits or other componentsconnected, arranged or grouped together, such as controllers,microprocessors, digital signal processors (“DSPs”), array processors,graphics or image processors, parallel processors, multiple coreprocessors, custom ICs, application specific integrated circuits(“ASICs”), field programmable gate arrays (“FPGAs”), adaptive computingICs, associated memory (such as RAM, DRAM and ROM), and other ICs andcomponents, whether analog or digital. As a consequence, as used herein,the term processor (or controller) should be understood to equivalentlymean and include a single IC, or arrangement of custom ICs, ASICs,processors, microprocessors, controllers, FPGAs, adaptive computing ICs,or some other grouping of integrated circuits which perform thefunctions discussed below, with associated memory, such asmicroprocessor memory or additional RAM, DRAM, SDRAM, SRAM, MRAM, ROM,FLASH, EPROM or EPROM. A processor 120 or controller 160, withassociated memory, may be adapted or configured (via programming, FPGAinterconnection, or hard-wiring) to perform the methodology of theinvention, as discussed herein. For example, the methodology may beprogrammed and stored, in a processor 120 or controller 160 with itsassociated memory (and/or memory 125) and other equivalent components,as a set of program instructions or other code (or equivalentconfiguration or other program) for subsequent execution when theprocessor or controller is operative (i.e., powered on and functioning).Equivalently, when the processor 120 or controller 160 may implementedin whole or part as FPGAs, custom ICs and/or ASICs, the FPGAs, customICs or ASICs also may be designed, configured and/or hard-wired toimplement the methodology of the invention. For example, the processor120 or controller 160 may be implemented as an arrangement of analogand/or digital circuits, controllers, microprocessors, DSPs and/orASICs, collectively referred to as a “processor” or “controller”, whichare respectively hard-wired, programmed, designed, adapted or configuredto implement the methodology of the invention, including possibly inconjunction with a memory 125.

The memory 125, which may include a data repository (or database), maybe embodied in any number of forms, including within any computer orother machine-readable data storage medium, memory device or otherstorage or communication device for storage or communication ofinformation, currently known or which becomes available in the future,including, but not limited to, a memory integrated circuit (“IC”), ormemory portion of an integrated circuit (such as the resident memorywithin a processor 120, controller 160 or processor IC), whethervolatile or non-volatile, whether removable or non-removable, includingwithout limitation RAM, FLASH, DRAM, SDRAM, SRAM, MRAM, FeRAM, ROM,EPROM or EPROM, or any other form of memory device, such as a magnetichard drive, an optical drive, a magnetic disk or tape drive, a hard diskdrive, other machine-readable storage or memory media such as a floppydisk, a CDROM, a CD-RW, digital versatile disk (DVD) or other opticalmemory, or any other type of memory, storage medium, or data storageapparatus or circuit, which is known or which becomes known, dependingupon the selected embodiment. The memory 125 may be adapted to storevarious look up tables, parameters, coefficients, other information anddata, programs or instructions (of the software of the presentinvention), and other types of tables such as database tables.

As indicated above, the processor 120 or controller 160 is hard-wired orprogrammed, using software and data structures of the invention, forexample, to perform the methodology of the present invention. As aconsequence, the system and method of the present invention may beembodied as software which provides such programming or otherinstructions, such as a set of instructions and/or metadata embodiedwithin a non-transitory computer readable medium, discussed above. Inaddition, metadata may also be utilized to define the various datastructures of a look up table or a database. Such software may be in theform of source or object code, by way of example and without limitation.Source code further may be compiled into some form of instructions orobject code (including assembly language instructions or configurationinformation). The software, source code or metadata of the presentinvention may be embodied as any type of code, such as C, C++, Matlab,SystemC, LISA, XML, Java, Brew, SQL and its variations (e.g., SQL 99 orproprietary versions of SQL), DB2, Oracle, or any other type ofprogramming language which performs the functionality discussed herein,including various hardware definition or hardware modeling languages(e.g., Verilog, VHDL, RTL) and resulting database files (e.g., GDSII).As a consequence, a “construct”, “program construct”, “softwareconstruct” or “software”, as used equivalently herein, means and refersto any programming language, of any kind, with any syntax or signatures,which provides or can be interpreted to provide the associatedfunctionality or methodology specified (when instantiated or loaded intoa processor or computer and executed, including the processor 120, 160,for example).

The software, metadata, or other source code of the present inventionand any resulting bit file (object code, database, or look up table) maybe embodied within any tangible, non-transitory storage medium, such asany of the computer or other machine-readable data storage media, ascomputer-readable instructions, data structures, program modules orother data, such as discussed above with respect to the memory 125,e.g., a floppy disk, a CDROM, a CD-RW, a DVD, a magnetic hard drive, anoptical drive, or any other type of data storage apparatus or medium, asmentioned above.

The network I/O interface circuit(s) 130 are utilized for appropriateconnection to a relevant channel, network or bus; for example, thenetwork I/O interface circuit(s) 130 may provide impedance matching,drivers and other functions for a wireline interface, may providedemodulation and analog to digital conversion for a wireless interface,and may provide a physical interface for the processor 120 or controller160 and/or memory 125 with other devices. In general, the network I/Ointerface circuit(s) 130 are used to receive and transmit data,depending upon the selected embodiment, such as program instructions,parameters, configuration information, control messages, data and otherpertinent information.

The wireless transmitters 135 and/or wireless transceivers 165 also maybe implemented as known or may become known in the art, to providewireless data communication to and/or from any other device, such aswireless or optical communication and using any applicable standard(e.g., any of the IEEE 802.11 standards, Global System for MobileCommunications (GSM), General Packet Radio Service (GPRS), cdmaOne,CDMA2000, Evolution-Data Optimized (EV-DO), Enhanced Data Rates for GSMEvolution (EDGE), Universal Mobile Telecommunications System (UMTS),Digital Enhanced Cordless Telecommunications (DECT), Digital AMPS(IS-136/TDMA), and Integrated Digital Enhanced Network (iDEN), WCDMA,WiFi, 3G, 4G, and LTE standards, for example and without limitation). Inaddition, the wireless transmitters 135 and/or wireless transceivers 165may also be configured and/or adapted to receive and/or transmit signalsexternally to the systems 200, 400 such as RF or infrared signaling, forexample, to receive information in real-time for output on a display,also for example and without limitation.

The network I/O interface circuit(s) 130 may be implemented as known ormay become known in the art, to provide data communication between theprocessor 120 or controller 160 and any type of network or externaldevice, such as wireless, optical, or wireline, and using any applicablestandard (e.g., one of the various PCI, USB, RJ 45, Ethernet (FastEthernet, Gigabit Ethernet, 300ase-TX, 300ase-FX, etc.), IEEE 802.11,WCDMA, WiFi, GSM, GPRS, EDGE, 3G and the other standards and systemsmentioned above, for example and without limitation), and may includeimpedance matching capability, voltage translation for a low voltageprocessor to interface with a higher voltage control bus, wireline orwireless transceivers, and various switching mechanisms (e.g.,transistors) to turn various lines or connectors on or off in responseto signaling from the processor 120 or controller 160. In addition, thenetwork I/O interface circuit(s) 130 may also be configured and/oradapted to receive and/or transmit signals externally to the systems200, 400 such as through hard-wiring or RF or infrared signaling, forexample, to receive information in real-time for output on a display,for example. The network I/O interface circuit(s) 130 may provideconnection to any type of bus or network structure or medium, using anyselected architecture. By way of example and without limitation, sucharchitectures include Industry Standard Architecture (ISA) bus, EnhancedISA (EISA) bus, Micro Channel Architecture (MCA) bus, PeripheralComponent Interconnect (PCI) bus, SAN bus, or any other communication orsignaling medium, such as Ethernet, ISDN, T1, satellite, wireless, andso on.

Numerous advantages of the representative embodiments are readilyapparent. The representative apparatus, method and/or system embodimentsprovide for noninvasive, ambulatory blood pressure and other vital signmonitoring. Representative apparatus and/or system embodiments arecomparatively unobtrusive, convenient and easy to use for an individualconsumer, while nonetheless being comparatively or sufficiently accurateto obtain meaningful results and actionable information, with acomparatively fast BP acquisition time. Representative apparatus and/orsystem embodiments also may provide improved compliance by being readilyintegrable into the user's daily activities. Depending on the selectedembodiment, such representative apparatus and/or system embodiments arereadily portable and/or wearable to provide ubiquitous monitoring allday and/or night, as may be necessary or desirable.

The present disclosure is to be considered as an exemplification of theprinciples of the invention and is not intended to limit the inventionto the specific embodiments illustrated. In this respect, it is to beunderstood that the invention is not limited in its application to thedetails of construction and to the arrangements of components set forthabove and below, illustrated in the drawings, or as described in theexamples. Systems, methods and apparatuses consistent with the presentinvention are capable of other embodiments and of being practiced andcarried out in various ways.

Although the invention has been described with respect to specificembodiments thereof, these embodiments are merely illustrative and notrestrictive of the invention. In the description herein, numerousspecific details are provided, such as examples of electroniccomponents, electronic and structural connections, materials, andstructural variations, to provide a thorough understanding ofembodiments of the present invention. One skilled in the relevant artwill recognize, however, that an embodiment of the invention can bepracticed without one or more of the specific details, or with otherapparatus, systems, assemblies, components, materials, parts, etc. Inother instances, well-known structures, materials, or operations are notspecifically shown or described in detail to avoid obscuring aspects ofembodiments of the present invention. In addition, the various Figuresare not drawn to scale and should not be regarded as limiting.

Reference throughout this specification to “one embodiment”, “anembodiment”, or a specific “embodiment” means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention and notnecessarily in all embodiments, and further, are not necessarilyreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics of any specific embodiment of the presentinvention may be combined in any suitable manner and in any suitablecombination with one or more other embodiments, including the use ofselected features without corresponding use of other features. Inaddition, many modifications may be made to adapt a particularapplication, situation or material to the essential scope and spirit ofthe present invention. It is to be understood that other variations andmodifications of the embodiments of the present invention described andillustrated herein are possible in light of the teachings herein and areto be considered part of the spirit and scope of the present invention.

It will also be appreciated that one or more of the elements depicted inthe Figures can also be implemented in a more separate or integratedmanner, or even removed or rendered inoperable in certain cases, as maybe useful in accordance with a particular application. Integrally formedcombinations of components are also within the scope of the invention,particularly for embodiments in which a separation or combination ofdiscrete components is unclear or indiscernible. In addition, use of theterm “coupled” herein, including in its various forms such as “coupling”or “couplable”, means and includes any direct or indirect electrical,structural or magnetic coupling, connection or attachment, or adaptationor capability for such a direct or indirect electrical, structural ormagnetic coupling, connection or attachment, including integrally formedcomponents and components which are coupled via or through anothercomponent.

With respect to signals, we refer herein to parameters that “represent”a given metric or are “representative” of a given metric, where a metricis a measure of a state of at least part of the regulator or its inputsor outputs. A parameter is considered to represent a metric if it isrelated to the metric directly enough that regulating the parameter willsatisfactorily regulate the metric. A parameter may be considered to bean acceptable representation of a metric if it represents a multiple orfraction of the metric.

Furthermore, any signal arrows in the drawings/Figures should beconsidered only exemplary, and not limiting, unless otherwisespecifically noted. Combinations of components of steps will also beconsidered within the scope of the present invention, particularly wherethe ability to separate or combine is unclear or foreseeable. Thedisjunctive term “or”, as used herein and throughout the claims thatfollow, is generally intended to mean “and/or”, having both conjunctiveand disjunctive meanings (and is not confined to an “exclusive or”meaning), unless otherwise indicated. As used in the description hereinand throughout the claims that follow, “a”, “an”, and “the” includeplural references unless the context clearly dictates otherwise. Also asused in the description herein and throughout the claims that follow,the meaning of “in” includes “in” and “on” unless the context clearlydictates otherwise.

The foregoing description of illustrated embodiments of the presentinvention, including what is described in the summary or in theabstract, is not intended to be exhaustive or to limit the invention tothe precise forms disclosed herein. From the foregoing, it will beobserved that numerous variations, modifications and substitutions areintended and may be effected without departing from the spirit and scopeof the novel concept of the invention. It is to be understood that nolimitation with respect to the specific methods and apparatusillustrated herein is intended or should be inferred. It is, of course,intended to cover by the appended claims all such modifications as fallwithin the scope of the claims.

It is claimed:
 1. A method of determining a blood pressure of a subjecthuman being for ambulatory monitoring, the method comprising: using apressure sensor array having a plurality of pressure sensorsspaced-apart in at least two dimensions, applanating an artery;receiving a plurality of pressure sensor signals, one or more of thepressure sensor signals having data representing amplitudes of one ormore arterial pressure waves; determining a frequency content of each ofthe one or more of the pressure sensor signals having data; selectingone or more periodic pressure sensor signals to form a first pluralityof selected pressure sensor signals; selecting one or more periodicpressure sensor signals within a selected deviation of a mean of thefirst plurality of selected pressure sensor signals to form a secondplurality of selected pressure sensor signals; using one or moreperiodic pressure sensor signals from the second plurality of selectedpressure sensor signals, determining a systolic blood pressure value anda diastolic blood pressure value.
 2. The method of claim 1, furthercomprising: for each periodic pressure sensor signal of the secondplurality of selected pressure sensor signals, determining across-coherence with each nearest neighbor pressure sensor signal; andselecting a periodic pressure sensor signal having a highest meancross-coherence.
 3. The method of claim 2, wherein the step ofdetermining the systolic blood pressure value and the diastolic bloodpressure value further comprises: determining the systolic bloodpressure value as a maximum of the periodic pressure sensor signalhaving a highest mean cross-coherence; and determining the diastolicblood pressure value as a minimum of the periodic pressure sensor signalhaving a highest mean cross-coherence.
 4. The method of claim 1, furthercomprising: performing a first filtering of the plurality of pressuresensor signals to eliminate one or more pressure sensor signals below apredetermined threshold.
 5. The method of claim 1, further comprising:using one or more periodic pressure sensor signals from the secondplurality of selected pressure sensor signals, determining a heart rate.6. The method of claim 1, wherein the step of determining the systolicblood pressure value and the diastolic blood pressure value furthercomprises: performing a Kalman filtering of the second plurality ofselected pressure sensor signals; determining the systolic bloodpressure value as a maximum of the Kalman filter data; and determiningthe diastolic blood pressure value as a minimum of the Kalman filterdata.
 7. An apparatus for determining a blood pressure of a subjecthuman being for ambulatory monitoring, the apparatus comprising: apressure sensor array having a plurality of pressure sensorsspaced-apart in at least two dimensions; and a processor coupled to thepressure sensor array, the processor adapted to receive a plurality ofpressure sensor signals, one or more of the pressure sensor signalshaving data representing amplitudes of one or more arterial pressurewaves; determine a frequency content of each of the one or more of thepressure sensor signals having data; select one or more periodicpressure sensor signals to form a first plurality of selected pressuresensor signals; select one or more periodic pressure sensor signalswithin a selected deviation of a mean of the first plurality of selectedpressure sensor signals to form a second plurality of selected pressuresensor signals; and using one or more periodic pressure sensor signalsfrom the second plurality of selected pressure sensor signals, determinea systolic blood pressure value and a diastolic blood pressure value. 8.The apparatus of claim 7, further comprising: a housing coupled to thepressure sensor array and to the processor; and a wearable attachmentcoupled to the housing.
 9. The apparatus of claim 7, wherein theprocessor is further adapted, for each periodic pressure sensor signalof the second plurality of selected pressure sensor signals, todetermine a cross-coherence with each nearest neighbor pressure sensorsignal; and select a periodic pressure sensor signal having a highestmean cross-coherence.
 10. The apparatus of claim 9, wherein theprocessor is further adapted to determine the systolic blood pressurevalue as a maximum of the periodic pressure sensor signal having ahighest mean cross-coherence; and determine the diastolic blood pressurevalue as a minimum of the periodic pressure sensor signal having ahighest mean cross-coherence.
 11. The apparatus of claim 7, wherein theprocessor is further adapted to perform a first filtering of theplurality of pressure sensor signals to eliminate one or more pressuresensor signals below a predetermined threshold.
 12. The apparatus ofclaim 7, wherein the processor is further adapted, using one or moreperiodic pressure sensor signals from the second plurality of selectedpressure sensor signals, to determine a heart rate.
 13. The apparatus ofclaim 7, wherein the processor is further adapted to perform a Kalmanfiltering of the second plurality of selected pressure sensor signals;determine the systolic blood pressure value as a maximum of the Kalmanfilter data; and determine the diastolic blood pressure value as aminimum of the Kalman filter data.
 14. The apparatus of claim 7, furthercomprising: a display for displaying the determined blood pressure valueand other vital sign information to the user.
 15. The apparatus of claim7, further comprising: a wireless transmitter to transmit the determinedblood pressure value and other vital sign information to a centrallocation.
 16. The apparatus of claim 7, further comprising: a networkinterface circuit to transmit the determined blood pressure value andother vital sign information to a central location.
 17. The apparatus ofclaim 7, further comprising: a memory circuit storing the determinedblood pressure value and other vital sign information.
 18. A system fordetermining a blood pressure of a subject human being for ambulatorymonitoring, the system comprising: a wearable apparatus comprising: apressure sensor array having a plurality of pressure sensorsspaced-apart in at least two dimensions, the pressure sensor arraygenerating a plurality of pressure sensor signals, one or more of thepressure sensor signals having data representing amplitudes of one ormore arterial pressure waves; and a wireless transmitter coupled to thepressure sensor array to transmit the plurality of pressure sensorsignals; a central monitor, comprising: a memory circuit; a wirelesstransceiver to receive the transmitted plurality of pressure sensorsignals; and a processor coupled to the wireless transceiver and to thememory, the processor adapted to a processor coupled to the pressuresensor array, the processor adapted to determine a frequency content ofeach of the one or more of the pressure sensor signals having data;select one or more periodic pressure sensor signals to form a firstplurality of selected pressure sensor signals; select one or moreperiodic pressure sensor signals within a selected deviation of a meanof the first plurality of selected pressure sensor signals to form asecond plurality of selected pressure sensor signals; and using one ormore periodic pressure sensor signals from the second plurality ofselected pressure sensor signals, determine a systolic blood pressurevalue and a diastolic blood pressure value.
 19. The system of claim 18,wherein the wearable apparatus further comprises: a housing coupled tothe pressure sensor array; and a wearable attachment coupled to thehousing.
 20. The system of claim 18, wherein the processor is furtheradapted to perform a first filtering of the plurality of pressure sensorsignals to eliminate one or more pressure sensor signals below apredetermined threshold; for each periodic pressure sensor signal of thesecond plurality of selected pressure sensor signals, to determine across-coherence with each nearest neighbor pressure sensor signal; toselect a periodic pressure sensor signal having a highest meancross-coherence; and to determine the systolic blood pressure value as amaximum of the periodic pressure sensor signal having a highest meancross-coherence; and determine the diastolic blood pressure value as aminimum of the periodic pressure sensor signal having a highest meancross-coherence.